Learn me: GM Gen V V8/6L80 as a swap candidate

Mrs STM has a 72 C10 that's in need of some updating. Free time is hard to come by, so I'd rather not deal with donor vehicles, or high mileage engines that would need extensive work. The goal is to buy a functional engine/trans "dropout" that I can easily set in place with minimal time investment. The end goal is to have a nice, updated cruiser rather than a race truck so no plans for power modification (As it is, the 350hp/380 ft-lbs from a stock L83 will be double the original 250 inline 6's output).

I'm in the information gathering phase now, and I'm seeing Gen V engines with the 6L80 for the same or even less than Gen IV engines with the 6l80. A 5.3L truck engine is the most likely unless a crazy good deal comes along on a 6.2L. It would remain almost entirely stock. Stock ECM is fine. Mounts/harness can be had just as easily as stuff for the older LS. The fuel tank and pump will require an upgrade no matter what engine goes in so that's a wash.

So what are the downfalls of the Gen V 5.3L/6L80 combo in general? Anything in particular that would make them poor candidates for a swap? Any stuff that I should look out for on powertrains with 75-125k miles on them? I'm no stranger to direct injection, and since it will remain stock I don't have too many concerns there. I don't remember hearing about fuel related issues with these. Is AFM that bad? And is it any better or worse than it was on the Gen IV stuff? I think I read a thread here about early transmission failures in this generation of trucks, but my hazy memory says that was the 8 speed trans, and not the 6 speeds. Does that sound right? Any other input?

In reply to STM317 :

I've replaced a bunch of injectors on these engines for misfires on start-up (P050D Cold Start Rough Idle). The AFM is worse on these than the Gen IV. You are pretty much guaranteed to have the valvetrain fly apart before 100k. Lifters that either collapse or break in half, broken valve springs, broken rocker arms, pushrods that are bent up like a banana. I've done way more valvetrain work on Gen Vs than Gen IVs. Its rare to see the camshaft itself be damaged, but it does happen. The guy next to me at work has one that he is putting a cam in currently. 

The 8-speeds were bad about a shudder when the torque converter went into lock up, sometimes a transmission flush fixed them, sometimes they need a torque converter. I'm not a transmission guy, but the 6-speeds do seem to have plenty of issues. I know I've diagnosed a few for noisy/weak front pumps.

The V6s looks like a sure thing (smaller/lighter, all aluminum 4.3, makes decent power too) but the junkyards around here are asking $4k for the thing.

ball out and get the 8.1

400 ft lbs off idle 

except parts are hard to come by and expensive 

I've got one in my 2016 Silverado 5.3 with 165k on it. I don't have any service records but it was a fleet truck that was clearly not babied.  I can see that the trans has been replaced since it's painted and there are witness marks on the bolts. I will say it moves the roughly 6000lbs quite well. 

Anecdotally my co-worker has done a trans but has not had AFM issues in 120k. Another friend had the AFM fail around 50k. 

I would think it would be worth doing an AFM delete while it's out. 

What about the 6 liter engine?  I feel like these are getting plentiful in the junkyards; they came on the 2500/3500 trucks and vans.  Earlier ones had a 4 speed 4l80E I believe; the later ones I think are 6 speeds. 

In reply to volvoclearinghouse :

They came in 2500s too. No AFM nonsense either.

volvoclearinghouse said:

What about the 6 liter engine?  I feel like these are getting plentiful in the junkyards; they came on the 3500/3500 trucks and vans.  Earlier ones had a 4 speed 4l80E I believe; the later ones I think are 6 speeds. 

I'd really prefer an aluminum block to keep weight off the nose. Hoping for more neutral handling and easier ride control as a result. I'd also like to avoid 15 year old engines that I'm likely to have to tear into because that takes time and draws the build out more than it needs to. I'm willing to pay to avoid that and save myself some time. That sticks me with a Gen IV 6.0L, and if I'm reading things correctly, it seems like all Gen IV 6.0L had AFM. Please correct me if I'm wrong here.

It also looks like an aluminum Gen IV 6.0/6l80 dropout is in the $5-7k range while a Gen V aluminum 5.3/6l80 combo is in the 3-5k range. The Gen V 5.3 appears to make the same or better power and torque as the older 6.0s, so if I'd have to deal with AFM either way then I don't see much benefit to the older, larger, more expensive engine.

I feel like I should expand a little on the intended purpose for the truck. It was my wife's grandfather's farm truck. There's some sentimentality to this truck for her as well as other members of the family, so I can't go too crazy.

Very low options (straight 6,3 on the tree,manual steering,manual brakes, no AC, etc). As such, it's a bear to drive, even for me. We'd like to update it so that it's easier and more comfortable to drive, therefore increasing the odds of actually using it. I'll also do what I can to make it safer and more reliable (3 pt belts, better lighting, moving the stock fuel tank, suspension update, etc). I don't really care about towing, or hauling, or 1/4 mile times, but if I can get more performance for the same or less money then I'll obviously consider that too. The truck will primarily be used as a nice weather daily driver and cruiser but I'm not expecting to put more than maybe 5-7k miles per year on it.

oops typing at same time !

What are you going to use the truck for ?

Towing a heavy trailer or just cruising and getting a few things at Home depot ?

and which newer V6-V8 rear wheel drive motors are alloy blocks and pretty bulletproof for pulling a 4000 pound trailer ?

If all you're going to do is putter around town with it, why not grab a vortec 350 and a 700R4 or something of that nature?  You can probably find them in junkyards and be out $1500 or so for the whole drivetrain.  The swap would be a pretty simple affair- the Vortec engines can be adapted to carburetors, too, so you wouldn't need to change any of the fuel system. 

In reply to volvoclearinghouse :

I'm not going junkyard parts picking with this one. Rebuilding an engine and trans takes time that I don't have. My goal is not to do this as cheaply as possible. The goal is to end up with a modern drivetrain that's reliable, relatively fuel efficient, and can work with as little hassle as possible for the next 20 years. If EV swaps were more mature, I might even consider that. But as it currentlys tands LS swaps and even LT swaps are pretty common in this chassis. It seems like I can buy high quality, off the shelf parts to make the swap as close to a bolt in affair as installing a modern engine into a 50 year old vehicle can be. The engine swap would be just one aspect of a more comprehensive update of the entire truck. I want to give it some of the advantages and amenities of a modern truck while retaining the same vintage aesthetic that's important to my wife and her family.

Ditching the stock fuel system is a large part of the appeal to a swap for me. The factory tank is vertical, right behind the seat back. I'm not a fan of  ~20 gallons of flammable liquid sloshing around right behind my wife's back without any kind of protection. I'm not a fan of noxious vapors potentially filling the same spot that my kid might ride in. The tank is getting moved behind the rear axle no matter what. It will be safer, and (coupled with an all aluminum engine) may even improve the weight balance/handling of the truck a little.

Back to the general topic of Gen V v8s, how effective are AFM disabling devices, rather than doing a full delete that would require a cam swap? What drawbacks do they have?

I think I'd be asking the Nelsons for some support in getting an Atlas 4200 six and related donor drivetrain four-speed automatic under the hood of that truck.  What's a decent running but otherwise beat Trailblazer donor go for these days, a grand?  

Im not a huge fan of L83 for an application like this. Id want simplicity and ease of repair.

The LY6 would be my recommendation. It still makes 360 hp on 87, but really once you unlock the PCM for the swap might as well get a tune and it will probably make just as much as the L83. No AFM. 6 Liters. Large port heads. Port injection instead of Direct Injection. Has VVT, which I like and tuned right makes a huge difference in the mid range.

You still get the 6 speed if thats what you want, but Im not a huge fan of them., Ive seen too many converter failures even at stock power, and if not caught early takes out the rest of the trans.

If the older engines werent such a sticking point for you. I legitamely believe an Lq4 or Lq9 with a 4l80e would be the easiest to swap, cheaper, and more reliable.

In reply to STM317 :

My understanding is that they may or may not be effective at preventing failure since the hard parts that fail are still in motor.  They work of the theory that since it's not being activated on and off it may prevent the hardware failure however those failures do still happen. 

I haven't installed one in mine since it seems one step above snake oil and at 165k it appears to be operating as intended. 

In reply to Greg Voth :

The AFM/DOD/TLA failures seem to happen right after they have been in V4 mode for a while.  Failure story always seem to start with "I was on a trip and pulled off the highway for gas and it started knocking/misfiring."

So locking them out in software and running permanently in V8 mode prevents the special lost motion lifters from lost-motioning, sticking or whatever happens inside from the valvetrain beating on the internals, and turning into permanent lost motion devices.

That said.... I really like the Gen V engines.  They seem to be engineered better packaging-wise and don't suffer from having to work with legacy SBC hardware like the Gen III/IV engines did.  And I kind of prefer DI from a technical standpoint.

Doesn't the 6L80E have its own ecu etc m

In reply to yupididit :

Yep.  IIRC having separate ECU/TCU started with the Gen IV timeframe.

In reply to Pete. (l33t FS) :

Yeah, I imagine they are less likely to fail with the software delete but from what I've read it's still pretty common. My friend doing the rebuild on the 50k mile motor had it deleted before 10k miles. 

Either way it'd be worth doing if he's not going to do the hardware delete.  I might go ahead and do mine just in case.

In reply to Greg Voth :

I'll admit part of the reason I think of a 5.3 swap for the RX-7 is for the AFM/DOD, because I like a little skosh more efficiency.  I don't expect the bottom end to last long enough for the valvetrain to fail, anyway.

The LS4 has a sweet spot of lightness and worthlessness, and I'm pretty sure I have a way to make it work in RWD fashion.  But hopefully the gallons and acres of Gen V 5.3s that Chevy has seen fit to flood the market with will depress prices on those a bunch, too.

I am not sure I understand the concern for aluminum vs iron here. It's a truck and there are likely other ways to shave 200# from it that are more cost effective. And front rear bias is probably insignificant if you aren't road racing or auto crossing. I would save the material premium and put it towards lower mileage/ better records.

itsarebuild said:

I am not sure I understand the concern for aluminum vs iron here. It's a truck and there are likely other ways to shave 200# from it that are more cost effective. And front rear bias is probably insignificant if you aren't road racing or auto crossing. I would save the material premium and put it towards lower mileage/ better records.

Noted. The thing is I'm hoping to avoid time sucking rebuilds, and most of the low mileage engines that I'd consider dropping in are new enough that they're aluminum anyway. Sure, I could go grab a cheap 350/350 combo or an inexpensive iron block Gen III or Gen IV with a 4l60 or 4l80, but those are old powertrains that likely have 200k+ on them by now. I know they're generally reliable engines, but I just can't justify dropping a powertrain into a vehicle with that kind of mileage on it without rebuilding things first. And rebuilding an engine and transmission erodes most (or all) of the initial cost savings of the cheaper powertrain, and adds precious time to the build. Between work and family/household obligations I'd be lucky to have a handful of hours each week to work on this project. I don't want to be building this thing for a decade. I'll pay a bit more for stuff that can be done with less overall time commitment.

There are different extremes on the powertrain donor spectrum. Cheap, old, high mileage engine/trans on one end, and expensive, brand new crate engines/trans on the other end. I'm looking for a sweet spot in between where reliable powertrains with a lot of life left in them can be dropped in without spending $10k+ on brand new stuff. I'm looking more for "plug and play" than "$20XX Challenge" here. I'd call Holley/Hooker and get their mounts, crossmembers, oilpan, and exhaust because they're well designed and work right the first time. I'd email Speartech and get a harness that works right the first time. I'd buy a Boyd's welding fuel tank with pump that fits right and just works properly out of the box. None of these are the cheapest options, but they're well designed, high quality pieces that should work right out of the box and require me to spend less time, money and energy cobbling stuff together.

So, it sounds like if I end up with an engine with AFM I've got three basic choices:

1) leave it alone and hope that things work out (potentially having to do expensive valve train work and a cam if there's a failure)

2) electronically disable AFM for a couple hundred bucks to reduce (but not eliminate) the chances of experiencing a failure

3) Go ahead and do the valve train/cam/tune work to delete AFM now instead of doing it all later when it's in the chassis.

My coworker just wrapped up lifters, pushrods and VLOM in a 2020 5.3L with 13,000 miles because of this. Wish I could say it was rare, but the new body style 2019+ trucks it often happens in the 4-digit mileage range